Inducing Cold-Sensitivity in the Frigophilic Fly Drosophila montana by RNAi

Abstract

Cold acclimation is a critical physiological adaptation for coping with seasonal cold. By increasing their cold tolerance individuals can remain active for longer at the onset of winter and can recover more quickly from a cold shock. In insects, despite many physiological studies, little is known about the genetic basis of cold acclimation. Recently, transcriptomic analyses in Drosophila virilis and D. montana revealed candidate genes for cold acclimation by identifying genes upregulated during exposure to cold. Here, we test the role of myo-inositol-1-phosphate synthase (Inos), in cold tolerance in D. montana using an RNAi approach. D. montana has a circumpolar distribution and overwinters as an adult in northern latitudes with extreme cold. We assessed cold tolerance of dsRNA knock-down flies using two metrics: chill-coma recovery time (CCRT) and mortality rate after cold acclimation. Injection of dsRNAInos did not alter CCRT, either overall or in interaction with the cold treatment, however it did induced cold-specific mortality, with high levels of mortality observed in injected flies acclimated at 5°C but not at 19°C. Overall, injection with dsRNAInos induced a temperature-sensitive mortality rate of over 60% in this normally cold-tolerant species. qPCR analysis confirmed that dsRNA injection successfully reduced gene expression of Inos. Thus, our results demonstrate the involvement of Inos in increasing cold tolerance in D. montana. The potential mechanisms involved by which Inos increases cold tolerance are also discussed.

Sex-specific responses to cold in a very cold-tolerant, northernDrosophila species

“…[35][36][37][38]. In particular, changes in lipids, fatty acids, and polyols have been shown to be important for cold adaptation in many insect taxa [6,7,39,40], including D. montana females [19,30,41]. This is consistent with the changes we identify here, including DE of previously identified candidate genes Inos and CG6910 [30,41].…”

“…In particular, changes in lipids, fatty acids, and polyols have been shown to be important for cold adaptation in many insect taxa [6,7,39,40], including D. montana females [19,30,41]. This is consistent with the changes we identify here, including DE of previously identified candidate genes Inos and CG6910 [30,41]. Both of these genes belong to the inositol biosynthetic pathway, emphasizing the importance of this pathway for surviving colder temperatures in D. montana.…”

Evolution of the metabolome in response to selection for increased immunity in populations of Drosophila melanogaster

“…However, the increase in lactate in the selected I populations is much lower, indicating that they have probably evolved ways to handle infection related stress. This is further supported by the fact that myoinositol which functions as messenger in signal transduction and helps in coping with stress [ 35 – 38 ] was also present in higher concentration in the selected populations.…”

The round goby genome provides insights into mechanisms that may facilitate biological invasions

“…Overland dispersal of fish eggs or larvae with boats or fishing gear involves air exposure, and indeed, round goby eggs withstand desiccation for up to 48 h [130]. Finally, osmolytes essentially act as anti-freeze agents and molecular chaperones and contribute to cryoprotection in diverse organisms from bacteria [131] to flies [132]. The surprising and unexpected ability of the round goby to colonize cold areas well below its temperature optimum of 22°C, such as the Northern Baltic Sea, may be linked to osmolyte production.…”